The present invention relates to a saw head raising/lowering winch and self-locking system for a sawmill. The sawhead vertical adjusting friction winch and self-locking system allows for easy, one-handed raising and lowering of the sawmill head within the sawmill and automatic saw head locking/brake.
There are several prior inventions for portable sawmills.
U.S. Pat. No. 5,784,941 describes a portable sawmill in which the functions of adjusting a cut and making a cut are divided between two separate devices. The invention discloses a vertical chain saw, ideally operated in an upward direction, which moves horizontally along a track, and, as such, does not require the raising or lowering of the chain saw relative to the track.
U.S. Pat. No. 5,243,892 discloses a portable sawmill with a frame base and an inverted U-shaped frame, supported by a carriage rolling along side tracks defined by the frame base. The chain saw is supported by a transversely slidable holder on the cross-beam of the frame. The chain saw is oriented in a vertical direction, and, in use, the log is placed on the U-shaped frame. The chain saw appears to be displaceable in the vertical direction through a vertical guide screw operated by a crank, said guide screw threadably engaging a slide block slidable across a cross beam. Due to the use of a guide screw, the chain saw does not require a tensioning mechanism or a brake on the vertical movement mechanism.
U.S. Pat. No. 4,640,170 discloses a portable sawmill with a frame that surrounds the log. The frame is dragged or slid along a frame supporting surface. The frame holds a chain saw at the two ends of its blade, in horizontal fashion, with chain saw support members. The invention uses sliding means for facilitating the movement of the frame over the log in a horizontal direction, but uses a vertical guide screw and crank mechanism for the vertical displacement of the saw head relative to the frame.
U.S. Pat. No. 4,275,632 describes a portable sawmill comprising a U-shaped support or carriage, holding a band saw. When in use, a log is placed between the two guide rails and is supported in place by a jacking mechanism with adjustable shelves. The band saw is in a generally horizontal position, and does not adjust in a vertical direction; instead, the log itself is moved up and down using a jacking mechanism.
U.S. Pat. No. 4,307,641 describes a portable sawmill comprising two skid rails, vertical support members, a pair of guide rails. The chain saw is held below the guide rails and can be adjusted in its vertical position relative to the skid rails using a set of vertical rod screws operated by a crank mechanism.
U.S. Pat. No. 4,235,140 describes a sawmill having a saw carriage having a vertical slide slidable on a vertical post of the sawmill frame, and adjustable vertically thereof by a cable secured at its upper end to a hook hooked into the top of the post. The lower end of the cable is attached to a reel, rotatable by a manual crank. The reel does not have any form of tensioning mechanism, but instead is fixed in place when the desired vertical location of the vertical slide is selected, using a latching bar which hooks into a path of pins keyed to a shaft on which the reel is mounted. Thus, the latching bar is raised in order to operate the reel (by rotating the reel using a manual crank), and the reel is locked in place by lowering the latching bar, which hooks between two pins, preventing rotational movement of the reel.
U.S. Pat. No. 3,965,788 describes a saw guide for use with a vertically operated portable chain saw. The saw guide comprises support means for the chain saw, to which the saw is attached. The vertical displacement of the chain saw along the support means is by way of a slidable engagement which can be clamped to a desired height using adjusting clamps.
U.S. Pat. No. 3,926,086 describes a portable sawmill that uses a complex pulley system to move the chain saw and supporting platform in a horizontal direction. Vertical displacement of the chain saw relative to the log and sawmill frame is through a pair of transversely-spaced vertically-movable racks having their lower ends operatively connected to the bar of the chain saw, a transverse shaft rotatably mounted on the frame, and a pair of transversely-spaced pinions fastened to the shaft and engaging the tracks. The racks and the attached chain saw is raised or lowered relative to the frame and to the log by rotation of the shaft.
U.S. Pat. No. 3,695,316 describes a portable timber milling jig that uses a carriage, holding a chain saw, axially surrounding a square guide rail. The chain saw is held at an approximately 45 degree angle and only uses one guide rail, and utilizes ball bearings on the carriage to move the carriage with respect to the guide rail. When in use, a log is placed under the guide rail. The carriage can be displaced vertically by sliding it along the guide rail, then can be locked into place.
U.S. Pat. No. 4,245,535 describes a portable sawmill with an elaborate hydraulic apparatus for cutting a log. The hydraulic apparatus, comprising a hydraulic rod and sleeve, is used to raise or lower the saw head relative to the platform.
The LumberLite™ 24 mid-size band sawmill and Lumbermate band sawmill (http://www.norwoodindustries.com) is a portable sawmill having two horizontal bases, each with a wheel assembly providing planar horizontal movement and fitted onto a set of rails of a sawmill base, two vertical saw supports extending vertically from the horizontal bases, and a top cross rail connecting the two vertical saw supports. The sawmill has a rotate rod extending between the vertical saw supports, with a crank handle. The crank handle rotates the rotate rod. The saw head is placed below the rotate rod and slildably affixed to the vertical saw supports such that it can move vertically along the two vertical saw supports. A cable extends between the rotate rod and the saw head, and reels around the rotate rod, lifting or lowering the saw head. The saw head is kept in place using clamps on the saw head affixing it to the vertical saw supports.
There is a need for an improved portable sawmill wherein the vertical displacement of the saw head relative to the carriage is simple, utilizes few moving parts, can be easily and accurately controlled with one hand despite the weight of the saw head, and can be locked and unlocked automatically without additional operator inputs.